In vitro profiling of opioid ligands using the cAMP formation inhibition assay and the β-arrestin2 recruitment assay: No two ligands have the same profile

Pharmacokinetics and Safety of Oliceridine Fumarate Injection in Chinese Patients with Chronic Non-Cancer Pain: A Phase I, Single-Ascending-Dose, Open-Label Clinical Trial

Background

Oliceridine is a novel G protein-biased ligand μ-opioid receptor agonist. This study aimed to assess the pharmacokinetics and safety profile of single-ascending doses of oliceridine fumarate injection in Chinese patients with chronic non-cancer pain.

Methods

Conducted as a single-center, open-label trial, this study administered single doses of 0.75, 1.5, and 3.0 mg to 32 adult participants. The trial was conducted in two parts. First, we conducted a preliminary test comprising the administration of a single dose of 0.75mg to 2 participants. Then, we conducted the main trial involving intravenous administration of escalating doses of oliceridine fumarate (0.75 to 3 mg) to 30 participants. Pharmacokinetic (PK) parameters were derived using non-compartmental analysis. Additionally, the safety evaluation encompassed the monitoring of adverse events (AEs).

Results

32 participants were included in the PK and safety analyses. Following a 2-min intravenous infusion of oliceridine fumarate injection (0.75, 1.5, or 3 mg), Cmax and Tmax ranged from 51.293 to 81.914 ng/mL and 0.034 to 0.083 h, respectively. AUC0-t and half-life (t1/2) increased more than proportionally with dosage (1.85-2.084 h). Treatment emergent adverse events (TEAEs) were found to be consistent with the commonly reported adverse effects of opioids, both post-administration and as documented in the original trials conducted in the United States. Critically, no serious adverse events were observed.

Conclusion

Oliceridine demonstrated comparable PK parameters and a consistent PK profile in the Chinese population, in line with the PK results observed in the original trials conducted in the United States. Oliceridine was safe and well tolerated in Chinese patients with chronic non-cancer pain at doses ranging from 0.75 mg to 3.0 mg.

Trial Registration

The trial is registered at chictr.org.cn (ChiCTR2100047180).

seco-1-Azacubane-2-carboxylic Acid: Derivative Scope and Comparative Biological Evaluation

The unusual and sterically constrained amino acid, seco-1-azacubane-2-carboxylic acid, was incorporated into a range of bioactive chemical templates, including enalaprilat, perindoprilat, endomorphin-2 and isoniazid, and subjected to biological testing. The endomorphin-2 derivative displayed increased activity at the δ opioid receptor, but a loss in activity was observed in the other cases, although human normal cell line evaluation suggests limited cytotoxic effects.

An Examination of the Complex Pharmacological Properties of the Non-Selective Opioid Modulator Buprenorphine

The goal of this review is to provide a recent examination of the pharmacodynamics as well as pharmacokinetics, misuse potential, toxicology, and prenatal consequences of buprenorphine. Buprenorphine is currently a Schedule III opioid in the US used for opioid-use disorder (OUD) and as an analgesic. Buprenorphine has high affinity for the mu-opioid receptor (MOR), delta (DOR), and kappa (KOR) and intermediate affinity for the nociceptin (NOR). Buprenorphine's active metabolite, norbuprenorphine, crosses the blood-brain barrier, is a potent metabolite that attenuates the analgesic effects of buprenorphine due to binding to NOR, and is responsible for the respiratory depressant effects. The area under the concentration curves are very similar for buprenorphine and norbuprenorphine, which indicates that it is important to consider this metabolite. Crowding sourcing has identified a buprenorphine street value (USD 3.95/mg), indicating some non-medical use. There have also been eleven-thousand reports involving buprenorphine and minors (age < 19) at US poison control centers. Prenatal exposure to clinically relevant dosages in rats produces reductions in myelin and increases in depression-like behavior. In conclusion, the pharmacology of this OUD pharmacotherapy including the consequences of prenatal buprenorphine exposure in humans and experimental animals should continue to be carefully evaluated.

Opioid-Modulated Receptor Localization and Erk1/2 Phosphorylation in Cells Coexpressing μ-Opioid and Nociceptin Receptors

We attempted to examine the alterations elicited by opioids via coexpressed μ-opioid (MOP) and nociceptin/orphanin FQ (NOP) receptors for receptor localization and Erk1/2 (p44/42 MAPK) in human embryonic kidney (HEK) 293 cells. Through two-photon microscopy, the proximity of MOP and NOP receptors was verified by fluorescence resonance energy transfer (FRET), and morphine but not buprenorphine facilitated the process of MOP-NOP heterodimerization. Single-particle tracking (SPT) further revealed that morphine or buprenorphine hindered the movement of the MOP-NOP heterodimers. After exposure to morphine or buprenorphine, receptor localization on lipid rafts was detected by immunocytochemistry, and phosphorylation of Erk1/2 was determined by immunoblotting in HEK 293 cells expressing MOP, NOP, or MOP+NOP receptors. Colocalization of MOP and NOP on lipid rafts was enhanced by morphine but not buprenorphine. Morphine stimulated the phosphorylation of Erk1/2 with a similar potency in HEK 293 cells expressing MOP and MOP+NOP receptors, but buprenorphine appeared to activate Erk1/2 solely through NOP receptors. Our results suggest that opioids can fine-tune the cellular localization of opioid receptors and phosphorylation of Erk1/2 in MOP+NOP-expressing cells.

Analgesic Opioid Ligand Discovery Based on Nonmorphinan Scaffolds Derived from Natural Sources

Strong opioid analgesics, including morphine, are the mainstays for treating moderate to severe acute pain and alleviating chronic cancer pain. However, opioid-related adverse effects, including nausea or vomiting, sedation, respiratory depression, constipation, pruritus (itch), analgesic tolerance, and addiction and abuse liability, are problematic. In addition, the use of opioids to relieve chronic noncancer pain is controversial due to the "opioid crisis" characterized by opioid misuse or abuse and escalating unintentional death rates due to respiratory depression. Hence, considerable research internationally has been aimed at the "Holy Grail" of the opioid analgesic field, namely the discovery of novel and safer opioid analgesics with improved opioid-related adverse effects. In this Perspective, medicinal chemistry strategies are addressed, where structurally diverse nonmorphinan-based opioid ligands derived from natural sources were deployed as lead molecules. The current state of play, clinical or experimental status, and novel opioid ligand discovery approaches are elaborated in the context of retaining analgesia with improved safety and reduced adverse effects, especially addiction liability.

Activation of the μ-opioid receptor by alicyclic fentanyls: Changes from high potency full agonists to low potency partial agonists with increasing alicyclic substructure

Fentanyl analogs represent an important group of new psychoactive substances and knowing their efficacy and potency might assist in interpreting observed concentrations. The potency of fentanyl analogs can be estimated from in vitro studies and can be used to establish structure–activity relationships. In this study, recombinant CHO‐K1 cells (AequoScreen) expressing the human μ‐opioid receptor were used to establish dose–response curves via luminescent analysis for cyclopropyl‐, cyclobutyl‐, cyclopentyl‐, cyclohexyl‐, and 2,2,3,3‐tetramethylcyclopropylfentanyl (TMCPF), on three separate occasions, using eight different concentrations in an eight‐fold serial dilution in triplicates starting at ~60 μM. Fentanyl was used as a full agonist reference while morphine and buprenorphine were included for comparison. Cyclopropylfentanyl (EC₅₀ = 4.3 nM), cyclobutylfentanyl (EC50 = 6.2 nM), and cyclopentylfentanyl (EC₅₀ = 13 nM) were full agonists slightly less potent than fentanyl (EC₅₀ = 1.7 nM). Cyclohexylfentanyl (EC₅₀ = 3.1 μM, efficacy 48%) and TMCPF (EC₅₀ = 1.5 μM, efficacy 65%) were partial agonists less potent than morphine (EC₅₀ = 430 nM). Based on the results, cyclopropyl‐, cyclobutyl‐, and cyclopentylfentanyl would be expected to induce intoxication or cause fatal poisonings at similar concentrations to fentanyl, while the toxic or fatal concentrations of cyclohexylfentanyl and TMCPF would be expected to be much higher.

Classics in Chemical Neuroscience: Buprenorphine

Buprenorphine has not only had an interdisciplinary impact on our understanding of key neuroscience topics like opioid pharmacology, pain signaling, and reward processing but has also been a key influence in changing the way that substance use disorders are approached in modern medical systems. From its leading role in expanding outpatient treatment of opioid use disorders to its continued influence on research into next-generation analgesics, buprenorphine has been a continuous player in the ever-evolving societal perception of opioids and substance use disorder. To provide a multifaceted account on the enormous diversity of areas where this molecule has made an impact, this article discusses buprenorphine's chemical properties, synthesis and development, pharmacology, adverse effects, manufacturing information, and historical place in the field of chemical neuroscience.